Nargeot Romuald, Petrissans Christine, Simmers John
Universités Bordeaux 2, 1, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Bordeaux, 33076 France.
J Neurosci. 2007 Jul 25;27(30):8059-70. doi: 10.1523/JNEUROSCI.1950-07.2007.
Motivated behaviors comprise appetitive actions whose occurrence results partly from an internally driven incentive to act. Such impulsive behavior can also be regulated by external rewarding stimuli that, through learning processes, can lead to accelerated and seemingly automatic, compulsive-like recurrences of the rewarded act. Here, we explored such behavioral plasticity in Aplysia by analyzing how appetitive reward stimulation in a form of operant conditioning can modify a goal-directed component of the animal's food-seeking behavior. In naive animals, protraction/retraction cycles of the tongue-like radula are expressed sporadically with highly variable interbite intervals. In contrast, animals that were previously given a food-reward stimulus in association with each spontaneous radula bite now expressed movement cycles with an elevated frequency and a stereotyped rhythmic organization. This rate increase and regularization, which was retained for several hours after training, depended on both the reward quality and its contingency because accelerated, stereotyped biting was not induced in animals that had previously received a less-palatable food stimulus or had been subjected to nonassociative reward stimulation. Neuronal correlates of these learning-induced changes were also expressed in the radula motor pattern-generating circuitry of isolated buccal ganglia. In such in vitro preparations, moreover, manipulation of the burst frequency of the bilateral motor pattern-initiating B63 interneurons indicated that the regularization of radula motor pattern generation in contingently trained animals occurred separately from an increase in cycle rate, thereby suggesting independent processes of network plasticity. These data therefore suggest that operant conditioning can induce compulsive-like actions in Aplysia feeding behavior and provide a substrate for a cellular analysis of the underlying mechanisms.
动机性行为包括那些部分由内在驱动的行动激励而产生的欲求行为。这种冲动行为也可由外部奖励刺激来调节，通过学习过程，这些刺激可导致被奖励行为加速且看似自动、类似强迫性的重复出现。在此，我们通过分析操作性条件反射形式的欲求奖励刺激如何改变动物觅食行为的目标导向成分，来探究海兔中的这种行为可塑性。在未受过训练的动物中，舌状齿舌的伸展/回缩周期偶尔出现，咬食间隔高度可变。相比之下，之前每次自发齿舌咬食都伴有食物奖励刺激的动物，现在表现出频率升高且具有刻板节奏组织的运动周期。这种速率增加和规律化在训练后持续数小时，它既取决于奖励质量也取决于奖励的偶然性，因为在之前接受过不太可口食物刺激或遭受过非关联性奖励刺激的动物中，不会诱发加速、刻板的咬食行为。这些学习诱导变化的神经元相关性也在分离的口腔神经节的齿舌运动模式产生回路中表现出来。此外，在这种体外制备物中，对双侧运动模式起始B63中间神经元爆发频率的操控表明，在接受偶然训练的动物中，齿舌运动模式产生的规律化与周期速率的增加是分开发生的，从而提示网络可塑性的独立过程。因此，这些数据表明操作性条件反射可在海兔进食行为中诱发类似强迫性的行为，并为潜在机制的细胞分析提供了基础。
